Analysis of time series of terrestrial optical images for understanding gravitational instabilities
Abstract
Passive sensors such as Single Lens Reflex (SLR) cameras are increasingly being used for ground-based monitoring of geohazards. Compared to terrestrial laser scanner (TLS) or radar imaging (GB-InSAR) systems, cameras are low-priced while also ensuring high sensor resolution (>15 megapixel). Qualitative information can be extracted from images such as the identification of changes in the surface morphology or the weather conditions; quantitative information can also be inferred such as surface velocities or volumes being eroded.
Two use cases are analyzed: the quantification of the dynamic of slides, and the detection of changes in the morphology of rockfaces. The objective of this work is to develop, implement and test an automated image processing pipeline for the analysis of long time series. The processing pipeline is based on the MicMac open-source photogrammetric library. Several modules have been developed such as: - A pre-processing module allowing the selection of the optimal set of images among the complete time series; - A co-registration module allowing the correction of the camera movement induced by temperature, wind or soil changes - A change detection module allowing the quantification of surface displacement by applying hierarchical sub-pixel correlation techniques. Several possibilities of correlation strategy (incremental, sequential, pairwise and multiple pairwise) are embedded. - A geo-referencing module allowing the conversion of the displacement fields from the image geometry to the terrestrial geometry. The displacement fields being computed from the image time series are compared to in-situ data from point sensors such as total station measurements, and from remote sensors such as laser scanning. The pipeline will be presented and its performance evaluated for several unstable slopes of the French Alps. The time series of displacement fields are further correlated to forcing factors such as rainfall and temperature changes. Acknowledgements: This work is carried with the support of CIFRE / ANRT as part of a private-public partnership among the School and Observatory of Earth Sciences of University of Strasbourg and the SAGE Society. Additional support is provided by the Open Partial Agreement Major Hazards of Council of Europe.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.G51C0494M
- Keywords:
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- 9805 Instruments useful in three or more fields;
- GENERAL OR MISCELLANEOUSDE: 9820 Techniques applicable in three or more fields;
- GENERAL OR MISCELLANEOUSDE: 1294 Instruments and techniques;
- GEODESY AND GRAVITYDE: 1295 Integrations of techniques;
- GEODESY AND GRAVITY